Discharge Printing

           Discharge Printing is also called Extract Printing. This is a method

            of applying a design to dyed fabric by printing a color-destroying

            agent, such as chlorine or hydrosulfite, to bleach out a white or

            light pattern on the darker coloured ground. In color-discharge

            printing, a dye impervious to the bleaching agent is combined with

            it, producing a colored design instead of white on the dyed ground.

            Discharge printing has been around for decades. But only in the past

            7-8 years screen printers in the industry have recognized it

            seriously. In the early years of discharge printing, the finished

            discharge print needed to be steamed during the drying process. This

            discouraged the use of discharge systems in the finished garment

            arena. The newly developed discharge ink systems are chemically

            reactive and dont need to be steam-neutralized. This advancement

            opened the door to discharge printing for the average screen

printer.

            Discharge printing has the ability to make bright, opaque colors on

            dark fabrics with a soft hand. Years ago the idea of opaque colors

            on dark fabrics and soft hand couldnt co-exist.

            Successful light-on-dark printing with plastisol relies on increased

            pigment loads, fillers and other additives to block out the color of

            the garment. Discharge inks modify the garment color by removing the

            garment color and replacing it with the new ink color. In simple

            terms, the discharge ink "bleaches" out the dye in the garment, thus

            allowing the pigment in the ink to absorb into the shirt fibers.

            The real magic of discharge printing can be witnessed when printing

            four-color process on black 100% cotton shirts. The print before

            curing appears very transparent. One can barely see the print until

            the garment exits the oven chamber, where the results can be quite

            remarkable: bright, vivid colors with a soft hand.

            The graphics on the casino gaming tables are printed with discharge

            inks to avoid the interference of the printed line with the roll of

            the dice. If the ink on these tables were printed with plastisol,

            the ink film (because it is a surface print) would change the speed

            and direction of the dice, thus changing the way the dice land.

            Discharge ink, on the other hand, provides a dyed-in-the-fabric

            result, keeping the playing surface smooth.

            The decrease in the production time is the biggest bonus of all. The

            fact that you can skip flash curing completely saves hours of

            production time and eliminates registration problems between the

            designs colors and the white printer under base used in normal

            printing on blacks.

            However, flash curing can be used in conjunction with discharge

            printing when printing discharge as an under base.

            Cleaner and more transparent inks can also be printed onto dark

            garments with the help of discharge additives. Early discharge

            additives were designed only for water base inks, but plastisol

            additives are available.

            Characteristics that indicate a garment will work with discharge ink

              The garment has to be made of natural fibers (100% cotton)

              The dye used in the garment must be dischargeable. The best

              results are achieved with garments that are 100% cotton and dyed

              with a reactive dye.

              The garment should not have been over dyed (when fabric is re-dyed

              to another color). This often happens because of a shortage of a

              certain fabric color or, in many cases, because quality control

              rejected the fabric color. These rejected colors are then over

              dyed with a black dye, which will bring nightmares to life when

              trying to use discharge inks. The discharge ink might discharge

              the black dye - only to reveal a phantom color underneath.

            Always test your garment to see if it is suitable for discharge

            printing. If you are a major printer doing large-volume printing, be

            aware that the shirts you order from the mill are tracked by lot

            numbers and it is possible that a completely different dye may be

            used from one lot to the next. Let your sales representative know

            that you are doing discharge printing and mention in writing that

            you need a dischargeable garment.

            Points to be noted

              Do not to overlap your separations if you want to print clean spot

              colors. Butt-to-butt separations are ideal for most discharge

              printing.

              Work with a negative background and allow the dark background of

              the garment to show through. If you choose to overlap the color

              separations, overlap the primary colors - red, blue and yellow -

              to achieve secondary and tertiary colors within the design.

              To create the screen for under-basing with discharge ink, sandwich

              all the color separations together (make a contact sheet or a

              mask) to allow the discharge ink to be printed under all

              subsequent colors. (Suitable plastisols can be printed over clear

              discharge bases. Consult your ink manufacturer for compatibility

              with plastisol.)

              Discharge printing is frequently used for all-over prints because

              of its soft hand.